1. Field of the Invention
The present invention relates to a two-core parallel extrafine coaxial cable having two parallel cores in which the outside peripheries of internal conductors are covered with insulators, and more particularly, to a two-core parallel extrafine coaxial cable longitudinally provided with a vapor-deposited tape that is excellent in bending characteristics and has a high shield effect and an improved shield strip property.
2. Description of the Related Art
In general, a coaxial cable increases a metal volume (shield volume) by a technology of using a braided shield and further double shields as an external shield in order to improve a shield effect. This technology is similarly used also in a two-core parallel extrafine coaxial cable having two parallel cores in which the outer peripheries of internal conductors are covered with insulators.
The two-core parallel extrafine coaxial cable is available in such an arrangement that, for example, a braided shield is applied to the outer periphery of two cores disposed in parallel with each other as an external shield, and a composite tape, which is composed of a plastic tape having a vapor-deposited copper layer of at least one xcexcm thick formed on one surface thereof, is wound around the outer periphery of the braided shield such that the vapor-deposited copper layer faces the braided shield.
When the external shield of the extrafine coaxial cable is stripped to process a terminal, a stripping job is sequentially performed such that a jacket is stripped first, the cable is put into a solder bath and the stripped portion of the external shield is solidified with solder, a cut is made to the external shield, and then the external shield is pulled out.
In the external shield composed of the braided shield, however, a problem arises in that it is very difficult to strip the external shield because when the external shield is pulled out, the braided shield is made tight and the core is tightened thereby. Sometimes, the core may be broken. Further, in the braided shield, since wires are stranded, they greatly rub against one another, thereby an internal external conductor is liable to be broken.
A method of solving the above problem is to use a laterally-wound shield in place of the braided shield. However, this method has a problem in that a coaxial cable employing the laterally-wound shield is inferior to that employing the braided shield in the shield effect because a shield volume is small.
Accordingly, an object of the present invention is to provide a two-core parallel extrafine coaxial cable longitudinally provided with a vapor-deposited tape that is excellent in bending characteristics and has a high shield effect and an improved shield strip property.
The present invention has been devised to achieve the above object.
According to a first aspect of the invention, a double-laterally-wound two-core parallel extrafine coaxial cable is composed of two cores having internal conductors whose outer peripheries are covered with insulators and disposed in parallel with each other, a first laterally-wound shield applied to the outer periphery of the two cores, a second laterally-wound shield applied to the outer periphery of the first laterally-wound shield in a direction opposite to that of the first laterally-wound shield, a composite tape, which is composed of a plastic tape having a vapor-deposited metal layer formed on one surface thereof, wound around the outer periphery of the second laterally-wound shield such that the vapor-deposited metal layer faces the second laterally-wound shield, and a jacket covering the outer periphery of the composite tape.
According to a second aspect of the invention, a double-laterally-wound two-core parallel extrafine coaxial cable is composed of two cores having internal conductors whose outer peripheries are covered with insulators and disposed in parallel with each other, a first laterally-wound shield applied to the outer periphery of the two cores, a second laterally-wound shield applied to the outer periphery of the first laterally-wound shield in a direction opposite to that of the first laterally-wound shield, a composite tape, which is composed of a plastic tape having vapor-deposited metal layers formed on both the surfaces thereof, wound around the outer periphery of the second laterally-wound shield, and a jacket covering the outer periphery of the composite tape.
According to a third aspect of the invention, a double-laterally-wound two-core parallel extrafine coaxial cable is composed of two cores having internal conductors whose outer peripheries are covered with insulators and disposed in parallel with each other, a first laterally-wound shield applied to the outer periphery of the two cores, a second laterally-wound shield applied to the outer periphery of the first laterally-wound shield in the same direction as that of and at a pitch different from that of the first laterally-wound shield, a composite tape, which is composed of a plastic tape having a vapor-deposited metal layer formed on one surface thereof, wound around the outer periphery of the second laterally-wound shield such that the vapor-deposited metal layer faces the second laterally-wound shield, and a jacket covering the outer periphery of the composite tape.
According to a fourth aspect of the invention, a double-laterally-wound two-core parallel extrafine coaxial cable is composed of two cores having internal conductors whose outer peripheries are covered with insulators and disposed in parallel with each other, a first laterally-wound shield applied to the outer periphery of the two cores, a second laterally-wound shield applied to the outer periphery of the first laterally-wound shield in the same direction as that of and at a pitch different from that of the first laterally-wound shield, a composite tape, which is composed of a plastic tape having vapor-deposited metal layers formed on both the surfaces thereof, wound around the outer periphery of the second laterally-wound shield, and a jacket covering the outer periphery of the composite tape.
It is preferable that the internal conductors of the cores have an outside diameter of about 0.13 mm or less and an outside diameter of 1.0 mm or less in a long axis direction when the cable is covered with the jacket.
It is preferable that vapor-deposited metal layer formed on the composite film be composed of one of silver and copper and have a thickness of 0.1 xcexcm or more.